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Possible dinosaur DNA has been found

scientificamerican.com

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Re: Possible dinosaur DNA has been found

#51

Post by RedComet »

echelon wrote: post #23
RedComet wrote: post #4

I love how not only the time of existence but also its size and appearance are presented as undisputable facts.

> I love how not only the time of existence but also its size and appearance are presented as undisputable facts. All evidence and models across a large variety of disciplines points to the age of the fossils. Geological strata, carbon isotope ratios, phylogenetics, etc. Feel free to present your evidence so that we can weigh in.

Unfortunately, unlike the author of the first reply implied, I don't have a grand religious take on the issue. I'm simply criticizing what passes for "science" these days. Even if someone grants you all of the evidence you presented, we see regularly that discoveries of this sort are false - be it from contamination in the lab or just an overzealous lab coat.

That said, I can give you a tasty nugget if you want. I reject using uniformitarianism (ad infinitum) as a scientific axiom. And I scoff at the arrogance of my fellow academics, especially for presenting stories such as these as fact.

Re: Possible dinosaur DNA has been found

#52

Post by daemonk »

burtonator wrote: post #49
tynpeddler wrote: post #15

Earlier quoted context omitted.

Homology studies. A DNA strand 17 bp long is pretty distinct. If a strand that long or longer was found, we would gain a lot of information about the evolutionary history of dinosaurs that we could never get from fossils. However, the article isn't clear about what they found. It says DNA, then it says there may not be a recoverable sequence. In that case nucleic acids would be a better term than DNA. Without more in…

There was a paper not long ago saying that the DNA half life is about 500k years or so and that most of the DNA would be degraded. The issue I had with this is why can't we reassemble chunks of DNA like we can with a puzzle. I'm certain specialized algorithms exist within DNA analysis for this reason. This isn't my field and there are already algorithms that exist on the top of my head that could solve this issue. Th…

That's pretty much how modern genome assemblies work. We currently do not have a reliable or accurate way of sequencing DNA longer than ~200 bases. So we fragment the DNA into small pieces, sequence them and then put it all back together.

It's not a completely solved problem as there are features of genomes that can make this process difficult or complicated (repetitive regions, highly heterozygous organisms, etc). Especially with short sequences.

We have technology right now that can allow us to sequence long fragments, but at lower quality and accuracy. There are a lot of tools out there that uses the longer, but lower quality sequences to scaffold the shorter, higher quality sequencing data.

Re: Possible dinosaur DNA has been found

#53

Post by hyperbovine »

phiresky wrote: post #36
aphextron wrote: post #8

Earlier quoted context omitted.

It's a completely impossible fantasy. DNA has a half life of ~500 years. Mammoths only died out around 10,000 years ago, which is why it's conceivable that one could be brought back, but all dinosaur DNA has been destroyed for millions of years.

> DNA has a half life of ~500 years but: Researchers in 2016 measured chloroplast DNA in marine sediment cores, and found diatom DNA dating back to 1.4 million years.[62] This DNA had a half-life significantly longer than previous research, of up to 15,000 years. Kirkpatrick's team also found that DNA only decayed along a half-life rate until about 100 thousand years, at which point it followed a slower, power-law de…

> and found diatom DNA dating back to 1.4 million years.

Okay, so you're 1/45th of the way there.

Re: Possible dinosaur DNA has been found

#54

Post by hyperbovine »

Baeocystin wrote: post #35
zabeltech wrote: post #14

Earlier quoted context omitted.

What if the DNA was frozen?

At these time scales, background radiation is the fundamental killer, and it is omnipresent in the environment. Using numbers taken from http://news.mit.edu/1994/safe-0105 for napkin-math: Average background dose/year: 500 millirem LD50 instantaneous exposure: 450000 millirem LD100 instantaneous exposure: 600000 millirem Radiation exposure of our dinoDNA sample: 65 million * 500 = 32.5 billion millirem. Obviously the…

At least on the ancient DNA projects I've worked on, the main obstacles have been a) deamination, b) fragmentation, and c) environmental contamination. Maybe radiation enters the picture at Jurassic timescales, but the DNA would become completely degraded and worthless tens millions of years before that. Unless they somehow managed to find a dinosaur frozen at about 0K, I'm extremely skeptical of these claims.

Re: Possible dinosaur DNA has been found

#55

Post by Robotbeat »

crimsonalucard wrote: post #32
tynpeddler wrote: post #15

Earlier quoted context omitted.

Homology studies. A DNA strand 17 bp long is pretty distinct. If a strand that long or longer was found, we would gain a lot of information about the evolutionary history of dinosaurs that we could never get from fossils. However, the article isn't clear about what they found. It says DNA, then it says there may not be a recoverable sequence. In that case nucleic acids would be a better term than DNA. Without more in…

I think by what "good does that do?" he means like what's the point if you can't use it to create dinosaur clones Jurassic Park style. I literally clicked on the link because that was the only thing on my mind. Not joking.

Even this amount of genetic material is a fantastic find, though. Maybe there's hope of some future technique being able to recover short sequences somehow.

Re: Possible dinosaur DNA has been found

#56

Post by jessriedel »

burtonator wrote: post #49
tynpeddler wrote: post #15

Earlier quoted context omitted.

Homology studies. A DNA strand 17 bp long is pretty distinct. If a strand that long or longer was found, we would gain a lot of information about the evolutionary history of dinosaurs that we could never get from fossils. However, the article isn't clear about what they found. It says DNA, then it says there may not be a recoverable sequence. In that case nucleic acids would be a better term than DNA. Without more in…

There was a paper not long ago saying that the DNA half life is about 500k years or so and that most of the DNA would be degraded. The issue I had with this is why can't we reassemble chunks of DNA like we can with a puzzle. I'm certain specialized algorithms exist within DNA analysis for this reason. This isn't my field and there are already algorithms that exist on the top of my head that could solve this issue. Th…

That's the halflife of each bond between nucleotides. After one tenth of a half life you're left with strands of average length ~20 nucleotides. After a full half life they are of length ~2, i.e., mostly just scattered GCs, ATs, etc. After several half-lives, it's almostly completely single nucleotides, and the chance that there are any surviving strands longer than a given length N falls exponentially in time and N.

Re: Possible dinosaur DNA has been found

#58

Post by stanfordkid »

thaumasiotes wrote: post #50
Retric wrote: post #45

Earlier quoted context omitted.

It would be a reasonable thing to attempt with today’s technology, but it would be a serious R&D project. It’s harder the older the sample and vastly more difficult if few closely related species survive.

> It would be a reasonable thing to attempt with today’s technology, but it would be a serious R&D project. Dinosaurs have enough cultural prestige that it would make total sense to do it as a vanity project if the technology is there. Similar to turning lead into gold -- there's enough cultural meaning built up around it that someone should do it before it really makes sense in a vacuum.

A project like this could be the space race of our epoch!

Re: Possible dinosaur DNA has been found

#59

Post by Robotbeat »

burtonator wrote: post #49
tynpeddler wrote: post #15

Earlier quoted context omitted.

Homology studies. A DNA strand 17 bp long is pretty distinct. If a strand that long or longer was found, we would gain a lot of information about the evolutionary history of dinosaurs that we could never get from fossils. However, the article isn't clear about what they found. It says DNA, then it says there may not be a recoverable sequence. In that case nucleic acids would be a better term than DNA. Without more in…

There was a paper not long ago saying that the DNA half life is about 500k years or so and that most of the DNA would be degraded. The issue I had with this is why can't we reassemble chunks of DNA like we can with a puzzle. I'm certain specialized algorithms exist within DNA analysis for this reason. This isn't my field and there are already algorithms that exist on the top of my head that could solve this issue. Th…

What does half life of 500,000 years mean? Does that mean any given gene will, on average, split every 500,000 years? Or become unusable in 500,000 years?

65 million years would mean 130 halvings. Basically nothing left, then.

...but this may depend on environmental conditions. this must depend on average environmental temperature, right? Might dinosaur specimens in Antarctic or Arctic regions have experienced significantly lower average environmental temperatures? That could increase the half life significantly.

Maybe we'll find Cryolophosaurus DNA some day...

EDIT: the DNA degradation study specimen was in the south island of New Zealand, which had an average burial temperature of 13C.

Antarctica along the coast has an average annual temperature of about -10C. Further inland and at higher elevation, it's much colder and dryer. Both those increase DNA stability. It's not crazy to me that you might have a factor of 100x greater stability for specimens found where the average temperature over the last 65 million years was 20-40 degrees colder and also dryer.

EDIT AGAIN: Just to support what I said, it seems like a difference of average burial temperature of just 2.5 degrees C doubles the half-life of DNA (and this is multiplicative), so with a 20 degree difference in average burial temperature, that would be 8 doublings of half-life length (factor of 256), so instead of 500,000 years until the DNA was all broken up, you could have 128 million years. https://figshare.com/articles/_Predicted_DNA_half_life_for_v...

Re: Possible dinosaur DNA has been found

#60

Post by dmurray »

BrandonM wrote: post #28
aphextron wrote: post #8

Earlier quoted context omitted.

It's a completely impossible fantasy. DNA has a half life of ~500 years. Mammoths only died out around 10,000 years ago, which is why it's conceivable that one could be brought back, but all dinosaur DNA has been destroyed for millions of years.

Bringing back mammoths based only on DNA seems to me to be akin to bringing back a New Yorker based only on DNA, thousands of years after NYC no longer exists. Even with perfect DNA, I think we underestimate the role that social structure and ecological momentum play in even the simplest of creatures. I think humans are the rule and not the exception when it comes to learning after birth. And that's not even getting…

> Even with perfect DNA, I think we underestimate the role that social structure and ecological momentum play in even the simplest of creatures.

I don't think that's true. We raise animals without their parents all the time, both on farms and in zoos. The animals we end up with are still recognizably horses or rats or chimpanzees, with unique behavioural traits that could be studied for years. Even if you lose the social structure of mammoth society, you would still be bringing back something fascinating.

Animals that can be hatched from eggs have even less dependency on their mothers, too.

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